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Agro-physiology of grasses and legumes destined for biorefining of protein – effects of defoliation and fertilization regimes

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Perennial herbaceous plants after defoliation follow one or a combination of two ‘reserve dependent’ regrowth strategies, to either photosynthesise with remaining leaves or halt root growth and remobilize stored assimilate when defoliation is severe (Wang et al., 2021). Their productivity thus integrates photosynthesis, soil nitrogen (N) uptake and internal remobilization, but remain poorly understood for different species subjected to fertilizer and defoliation regimes and targeting biorefining of feed protein. Field experiment was conducted from 2019 to 2021 on sandy soil in Denmark with either fertilized grasses (perennial ryegrass, tall fescue), unfertilized legumes (alfalfa, red clover) or their fertilized mixture (grass-legume), each defoliated in high (2), medium (4) or low frequency (6 weeks) at either 7-9 or 12-14 cm height. Differences between treatment means (excluding the establishment year 2019) were evaluated by mixed-effects model fitted to annual biomass and N yield. Grass species, defoliation frequency and height were highly significant factors for both biomass and N yield, whereas N fertilization as influential factor was likely offset by the unfertilized legumes, prompting for data analysis method integrating multiple two-way interactions as more suitable. The largest biomass was obtained by tall fescue (11.8-14.2 Mg ha-1) and grass-legume mixture (12.5-13.3 Mg ha-1), both defoliated at medium to low frequency, regardless of N fertilization and defoliation height. For N yield, the systems with red clover (395-440 kg N ha-1) and grass-clover mixture (360-400 kg N ha-1) defoliated at high to medium frequency were significantly more productive than the others. Within the season, the results clearly showed the contribution of the spring and main-season defoliation event to the annual biomass (Zhang et al., 2021). We also estimated canopy radiation use efficiency and measured extractable protein to elucidate to which extend it reflects the N yield and thus support the integration of environmental and economic sustainability of perennial systems targeting biorefining of feed protein. This study also provides novel insights in perennial productivity modulated in dynamic terms by management.
TitelProceedings of the XXI International Nitrogen Workshop. Halving nitrogen waste by 2030
RedaktørerL. Lassaletta, A. Sanz-Cobeña, C. Pinsard, S. Garde
Antal sider1
ForlagCEPADE-Universidad Politecnica de Madrid
Udgivelsesårnov. 2022
ISBN (Elektronisk)978-84-122114-6-7
StatusUdgivet - nov. 2022
BegivenhedThe XXI International Nitrogen Workshop. Halving nitrogen waste by 2030. - Madrid, Spanien
Varighed: 24 okt. 202228 okt. 2022


KonferenceThe XXI International Nitrogen Workshop. Halving nitrogen waste by 2030.

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